The present invention relates generally to a cutting apparatus and particularly to a rivet connection for a hedge cutting blade.
A hedge or brush cutting bar generally includes four basic components: a stationary blade, a movable cutting blade, a retaining blade, and a fastening mechanism for holding the retaining blade in position to suitably allow reciprocating movement of the cutting blade as captured between the stationary blade and retaining blade.
The stationary blade component attaches to the cutting device and includes a series of notches along its length. The movable cutting blade includes a corresponding series of notches along its length and lies in face to face relation to the stationary blade. By aligning the notches of the stationary and cutting blades, work pieces to be severed may be positioned within the severing space of the aligned notches of the stationary blade and the cutting blade. By reciprocating the cutting blade relative to the stationary blade, work pieces captured within the corresponding notches are severed as the notch edges slide in scissor like fashion. In this manner, hedge or brush material may be trimmed by moving the cutting bar through the body of the hedge.
The retaining blade component of the hedge cutting bar holds the reciprocating blade against the stationary blade. The reciprocating cutting blade is then captured between the stationary blade and the retaining blade. The fastening mechanism holds the retaining blade in position while suitably allowing reciprocal movement of the cutting blade. Such fastening means have previously been nut and bolt arrangements or straight sided rivets interconnecting the retaining blade and stationary blade, and passing through slots in the reciprocating cutting blade. The slots lie along the longitudinal axis of the cutting blade whereby reciprocal movement of the cutting blade is unencumbered by the bolt inserted therethrough. Also, spacing rings have been positioned within the slots to receive the bolts or rivets and allow the fastening arrangement to be tightened with sufficient force to secure the structure, but not pinch the cutting blade between the stationary blade and the retaining blade. More particularly, the spacer rings are thicker than the cutting blade so as to accept the tightening pressure of the nut and bolt rivet assemblies without restricting movement of the cutting blade.
Such hedge cutting devices operate at a high rate of reciprocation and are typically applied to hardy work material. Accordingly, the cutting blades experience great vibrational forces in severing such work pieces. The above-described fastening arrangement, i.e., nut, bolt or rivet and spacer assemblies, have proven successful, but only to a limited extent. The nut and bolt assemblies can loosen under the vibrational and operational forces imposed upon the hedge cutting bar. Such loosening requires operator monitoring and possibly intermittent tightening of the nut and bolt assemblies. While lock washers have been used to prevent the loosening, hedge cutting devices remain suspectable to this deficiency.
A second problem encountered with use of such spacer rings within the slots of the cutting blade relates to the manufacture of suitable spacer rings. More particularly, it is important that the set of spacer rings used in a given cutting blade be consistent in thickness. It is desirable that the spacer rings be slightly thicker than the thickness of the cutting blade, but when spacer rings have inconsistent thickness it is necessary to oversize the thickness of the spacer rings in order to avoid the undesirable pinching of the cutting blade between the retaining blade and the stationary blade. If the spacer rings are too thick poor cutting action results. Manufacture of spacing rings can include a preliminary manufacturing step wherein the body of the spacer ring is formed and a secondary step bringing the spacer ring into final, precise dimension. While such manufacturing methods might provide spacing rings of suitable, i.e., precise, thickness, the additional manufacturing steps requiring precise final dimensioning add to the cost of manufacture.
Accordingly, it would be desirable to provide a fastening mechanism for a hedge cutting device which suitably captures the reciprocating cutting blade between a stationary blade and a retaining blade while not unduly restricting movement of the cutting blade and not of inordinate manufacturing expense. The subject matter of the present invention provides such a fastening mechanism.